.alpha.-Oxolactams are useful synthons for preparing a variety of natural products and biologically active compounds (for example see A. Hisham Tetrahedron, 1997, 53, no. 5, 1813-1822). They can also be used to prepare synthetically useful .alpha.-substituted-.omega.-amino carboxilic acids, and to prepare a variety of isoindigoide dyes (G. Kollenz, et al. Tetrahedron, 1996, 52, no. 15, 5427-5440).
.alpha.-Oxo-.beta.-lactams, such as 6-oxopenams, 7-oxocephems and 6-oxopenems, are also useful for preparing .alpha.-alkylidene-.beta.-lactams and .alpha.-vinylidene-.beta.-lactams, both important classes of .beta.-lactamase inhibitors (U.S. Pat. No. 5,597,817, issued Jan. 29, 1997 ("817"); U.S. Pat. No. 5,629,306, issued May 13, 1997 ("306"); Buynak et al., J. Org. Chem., 1993, 58, 1325.; Buynak et al., J. Am. Chem. Soc., 1994, 116, 10955; Buynak et al., J. Med. Chem., 1995, 38, 1022; Buynak et al., Bioorg. Med. Chem. Lett., 1995, 5, 1513; Arisawa et al., J. Antibiot., 1982, 35, 1578; Brenner et al., Biochemistry, 1984, 23, 5839; Chen et al., Tetrahedron Lett., 1986, 27, 3449; Bennet et al., J. Antibiot., 1991, 44, 969.
.alpha.-Oxo-.beta.-lactams have also been used to prepare cytotoxic analogs of paclitaxel (J. Kant et al. Tetrahedron Letters, 1996, 37, 6495-6498); and to prepare .alpha.-aminoacid N-carboxy anhydrides and their corresponding .alpha.-amino acid derivatives (C. Palomo J. Org. Chem., 1994, 59, 3123-3130).
J. M. van der Veen et al. J. Org. Chem., 1989, 54, 5758-5762 disclose the preparation of specific .alpha.-oxo-.beta.-lactams by hydrolysis of the corresponding .alpha.-chloro-.alpha.-phenylthio-.beta.-lactams, which are prepared by the treatment of .alpha.-phenylthio-.beta.-lactams with N-chlorosuccinimide. C. Palomo et al. J. Org. Chem, 1994, 59, 3123-3130, disclose the preparation of specific .alpha.-oxo-.beta.-lactams by oxidation of the corresponding .alpha.-hydroxy-.beta.-lactams using Me.sub.2 SBr.sub.2 --NEt.sub.3, CrO.sub.3 -- pyridine, or DMSO-P.sub.2 O.sub.5. U.S. patents '817 and '306 disclose the preparation of specific .alpha.-oxo-.beta.-lactams by treatment of the corresponding .alpha.-amino-.beta.-lactams with trifluoromethanesulfonic anhydride and triethylamine, followed by aqueous acid.
Existing methods for preparing .alpha.-oxolactams are limited because they require the use of toxic or corrosive reagents, produce hazardous side products, require starting materials that are difficult or expensive to prepare, or yield products that can not be easily isolated or purified. Additionally, existing methods can not conveniently be preformed to yield products on a commercially useful (e.g. kilogram) scale. Therefore, there is a need for improved methods for preparing .alpha.-oxolactams, which overcome one or more of the limitations of the existing synthetic methods.